Noob isolastic question

A old time trick I stumbled across on a real slow idle smooth runing Combat was finding them staggered a few degrees, one retard the other advanced so unless one jug is way over advanced should not be detectable in vibration, just back fire tendency on starts. I a number of times taken off with a plug lead off one side and really didn't notice till noticing lack of pull and some uneven sounds at full hwy way speed but not much sense of vibration to alert me. These were just easy travel events not hole shot type hi throttle use that would of revealed missing a jug right away but lack of pull. A one lung Cdo can easy hold legal hwy speed but don't expect much passing ability.